Monday, January 31, 2011

NASA Satellite Tracks Menacing Australian Cyclone


Fresh on the heels of a series of crippling floods that began in December 2010, and a small tropical cyclone, Anthony, this past weekend, the northeastern Australian state of Queensland is now bracing for what could become one of the largest tropical cyclones the state has ever seen.

The Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua satellite, built and managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., captured this infrared image of Yasi on Jan. 31, 2011, at 6:29 a.m. PST (9:29 a.m. EST). The AIRS data create an accurate 3-D map of atmospheric temperature, water vapor and clouds, data that are useful to forecasters. The image shows the temperature of Yasi's cloud tops or the surface of Earth in cloud-free regions. The coldest cloud-top temperatures appear in purple, indicating towering cold clouds and heavy precipitation. The infrared signal of AIRS does not penetrate through clouds. Where there are no clouds, AIRS reads the infrared signal from the surface of the ocean waters, revealing warmer temperatures in orange and red.

The AIRS image shows deep convective (thunderstorm) bands wrapping tighter into the low-level circulation center. Wrapping bands of thunderstorms indicate strengthening.

At the approximate time this image was taken, Yasi had maximum sustained winds near 90 knots (166 kilometers per hour, or 103 mph), equivalent to a Category Two hurricane on the Saffir-Simpson Scale. It was centered about 1,400 kilometers (875 miles) east of Cairns, Australia, moving west at about 19 knots per hour (35 kilometers per hour, or 22 mph). Cyclone-force winds extend out to 48 kilometers (30 miles) from the center.

Yasi is forecast to move west, then southwestward, into an area of low vertical wind shear (strong wind shear can weaken a storm). Forecasters at the Joint Typhoon Warning Center expect Yasi to continue to strengthen over the next 36 hours. The Center forecasts a landfall just south of Cairns as a large 100-plus knot-per-hour (185 kilometers per hour, or 115 mph) system by around midnight local time on Wednesday, Feb. 2.

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Wednesday, January 26, 2011

Asteroids Ahoy! Jupiter Scar Likely from Rocky Body


A hurtling asteroid about the size of the Titanic caused the scar that appeared in Jupiter's atmosphere on July 19, 2009, according to two papers published recently in the journal Icarus.

Data from three infrared telescopes enabled scientists to observe the warm atmospheric temperatures and unique chemical conditions associated with the impact debris. By piecing together signatures of the gases and dark debris produced by the impact shockwaves, an international team of scientists was able to deduce that the object was more likely a rocky asteroid than an icy comet. Among the teams were those led by Glenn Orton, an astronomer at NASA's Jet Propulsion Laboratory, Pasadena, Calif., and Leigh Fletcher, researcher at Oxford University, U.K., who started the work while he was a postdoctoral fellow at JPL.

"Both the fact that the impact itself happened at all and the implication that it may well have been an asteroid rather than a comet shows us that the outer solar system is a complex, violent and dynamic place, and that many surprises may be out there waiting for us," said Orton. "There is still a lot to sort out in the outer solar system."

The new conclusion is also consistent with evidence from results from NASA's Hubble Space Telescope indicating the impact debris in 2009 was heavier or denser than debris from comet Shoemaker-Levy 9, the last known object to hurl itself into Jupiter's atmosphere in 1994.

Before this collision, scientists had thought that the only objects that hit Jupiter were icy comets whose unstable orbits took them close enough to Jupiter to be sucked in by the giant planet's gravitational attraction. Those comets are known as Jupiter-family comets. Scientists thought Jupiter had already cleared most other objects, such as asteroids, from its sphere of influence. Besides Shoemaker-Levy, scientists know of only two other impacts in the summer of 2010, which lit up Jupiter's atmosphere.

The July 19, 2009 object likely hit Jupiter between 9 a.m. and 11 a.m. UTC. Amateur astronomer Anthony Wesley from Australia was the first to notice the scar on Jupiter, which appeared as a dark spot in visible wavelengths. The scar appeared at mid-southern latitudes. Wesley tipped off Orton and colleagues, who immediately used existing observing time at NASA's Infrared Telescope Facility in Mauna Kea, Hawaii, the following night and proposed observing time on a host of other ground-based observatories, including the Gemini North Observatory in Hawaii, the Gemini South Telescope in Chile, and the European Southern Observatory's Very Large Telescope in Chile. Data were acquired at regular intervals during the week following the 2009 collision.

The data showed that the impact had warmed Jupiter's lower stratosphere by as much as 3 to 4 Kelvin at about 42 kilometers above its cloudtops. Although 3 to 4 Kelvin does not sound like a lot, it is a significant deposition of energy because it is spread over such an enormous area.

Plunging through Jupiter's atmosphere, the object created a channel of super-heated atmospheric gases and debris. An explosion deep below the clouds – probably releasing at least around 200 trillion trillion ergs of energy, or more than 5 gigatons of TNT -- then launched debris material back along the channel, above the cloud tops, to splash back down into the atmosphere, creating the aerosol particulates and warm temperatures observed in the infrared. The blowback dredged up ammonia gas and other gases from a lower part of the atmosphere known as the troposphere into a higher part of the atmosphere known as the stratosphere.

"Comparisons between the 2009 images and the Shoemaker-Levy 9 results are beginning to show intriguing differences between the kinds of objects that hit Jupiter," Fletcher said. "The dark debris, the heated atmosphere and upwelling of ammonia were similar for this impact and Shoemaker-Levy, but the debris plume in this case didn't reach such high altitudes, didn't heat the high stratosphere, and contained signatures for hydrocarbons, silicates and silicas that weren't seen before. The presence of hydrocarbons, and the absence of carbon monoxide, provide strong evidence for a water-depleted impactor in 2009."

The detection of silica in this mixture of Jovian atmospheric gases, processed bits from the impactor and byproducts of high-energy chemical reactions was significant because abundant silica could only be produced in the impact itself, by a strong rocky body capable of penetrating very deeply into the Jovian atmosphere before exploding, but not by a much weaker comet nucleus. Assuming that the impactor had a rock-like density of around 2.5 grams per cubic centimeter (160 pounds per cubic foot), scientists calculated a likely diameter of 200 to 500 meters (700 to 1,600 feet).

Scientists computed the set of possible orbits that would bring an object into Jupiter in the right range of times and at the right locations. Then they searched the catalog of known asteroids and comets to find the kinds of objects in these orbits. An object named 2005 TS100 – which is probably an asteroid but could be an extinct comet – was one of the closest matches. Although this object was not the actual impactor, it has a very chaotic orbit and made several very close approaches to Jupiter in computer models, demonstrating that an asteroid could have hurtled into Jupiter.

"We weren't expecting to find that an asteroid was the likely culprit in this impact, but we've now learned Jupiter is getting hit by a diversity of objects," said Paul Chodas, a scientist at NASA's Near-Earth Object Program Office at JPL. " Asteroid impacts on Jupiter were thought to be quite rare compared to impacts from the so-called 'Jupiter-family comets,' but now it seems there may be a significant population of asteroids in this category."

Scientists are still working to figure out what that frequency at Jupiter is, but asteroids of this size hit Earth about once every 100,000 years. The next steps in this investigation will be to use detailed simulations of the impact to refine the size and properties of the impactor, and to continue to use imaging at infrared, as well as visible wavelengths, to search for debris from future impacts of this size or smaller.

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Monday, January 24, 2011

NASA's Salt-Seeking Instrument Gets a Silvery Blanket


Technicians from NASA's Jet Propulsion Laboratory in Pasadena, Calif., completed the installation of thermal blankets on NASA's Aquarius instrument last week, as the Aquarius/Satelite de Aplicaciones Cientificas (SAC-D) spacecraft continued functional performance tests at Brazil's National Institute for Space Research (Laboratório de Integração e Testes – Instituto Nacional de Pesquisas Espaciais, or LIT-INPE) in Sáo José dos Campos.

Activities are proceeding on schedule for shipment of the spacecraft to California's Vandenberg Air Force Base in late March for a launch in early June.

Aquarius/SAC-D is an international mission involving NASA and Argentina's space agency, Comisión Nacional de Actividades Espaciales. Aquarius, the primary instrument on the mission, was built jointly by JPL and NASA's Goddard Space Flight Center, Greenbelt, Md. It will provide monthly global maps of how the concentration of dissolved salt (known as salinity) varies on the ocean surface. Salinity is a key tracer for understanding the ocean's role in Earth's water cycle and understanding ocean circulation.

By measuring ocean salinity from space, Aquarius will provide new insights into how the massive natural interplay of freshwater moving among the ocean, atmosphere and sea ice influences Earth's ocean circulation, weather and climate.

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Sunday, January 23, 2011

A Supermassive Black Hole


In a single exposure, astronomers were able to confirm the existence of a supermassive black hole in the center of galaxy M84. They did this by using the Hubble Space Telescope's more powerful spectrograph to map the rapid rotation of gas at the galaxy's center. The colorful zigzag provides the evidence. If no black hole were present, the line would be nearly vertical. The Space Telescope Imaging Spectrograph measured a velocity of 880,000 mph within 26 light-years of the galaxy's center. This measurement allowed astronomers to calculate that the black hole contains at least 300 million solar masses. M84 is located in the Virgo Cluster of galaxies, 50 million light-years from Earth, and a nearby neighbor to the more massive M87 galaxy, which also contains an extremely massive black hole. The image on the left shows the galaxy's center in visible light.

This image was originally released May 12, 1997.

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Thursday, January 20, 2011

Mars Sliding Behind Sun After Rover Anniversary


The team operating NASA's Mars rover Opportunity will temporarily suspend commanding for 16 days after the rover's seventh anniversary next week, but the rover will stay busy.

For the fourth time since Opportunity landed on Mars on Jan. 25, 2004, Universal Time (Jan. 24, Pacific Time), the planets' orbits will put Mars almost directly behind the sun from Earth's perspective.

During the days surrounding such an alignment, called a solar conjunction, the sun can disrupt radio transmissions between Earth and Mars. To avoid the chance of a command being corrupted by the sun and harming a spacecraft, NASA temporarily refrains from sending commands from Earth to Mars spacecraft in orbit and on the surface. This year, the commanding moratorium will be Jan. 27 to Feb. 11 for Opportunity, with similar periods for the Mars Reconnaissance Orbiter and Mars Odyssey orbiter.

Downlinks from Mars spacecraft will continue during the conjunction period, though at a much reduced rate. Mars-to-Earth communication does not present risk to spacecraft safety, even if transmissions are corrupted by the sun.

NASA's Mars Reconnaissance Orbiter will scale back its observations of Mars during the conjunction period due to reduced capability to download data to Earth and a limit on how much can be stored onboard.

Opportunity will continue sending data daily to the Odyssey orbiter for relay to Earth. "Overall, we expect to receive a smaller volume of daily data from Opportunity and none at all during the deepest four days of conjunction," said Alfonso Herrera, a rover mission manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

The rover team has developed a set of commands to be sent to Opportunity in advance so that the rover can continue science activities during the command moratorium.

"The goal is to characterize the materials in an area that shows up with a mineralogical signal, as seen from orbit, that's different from anywhere else Opportunity has been," said JPL's Bruce Banerdt, project scientist for Opportunity and its rover twin, Spirit. The area is at the southeastern edge of a crater called "Santa Maria," which Opportunity approached from the west last month.

Drives last week brought Opportunity to the position where it will spend the conjunction period. From that position, the rover's robotic arm can reach an outcrop target called "Luis de Torres." The rover's Moessbauer spectrometer will be placed onto the target for several days during the conjunction to assess the types of minerals present. The instrument uses a small amount of radioactive cobalt-57 to elicit information from the target. With a half-life of less than a year, the cobalt has substantially depleted during Opportunity's seven years on Mars, so readings lasting several days are necessary now to be equivalent to much shorter readings when the mission was newer.

Opportunity will also make atmospheric measurements during the conjunction period. After conjunction, it will spend several more days investigating Santa Maria crater before resuming a long-term trek toward Endurance crater, which is about 22 kilometers (14 miles) in diameter and, at its closest edge, about 6 kilometers (4 miles) from Santa Maria.

Opportunity's drives to the southeastern edge of Santa Maria brought the total distance driven by the rover during its seventh year on Mars to 7.4 kilometers (4.6 miles), which is more than in any previous year. The rover's total odometry for its seventh anniversary is 26.7 kilometers (16.6 miles).

Opportunity and Spirit, which landed three weeks apart, successfully completed their three-month prime missions in April 2004, then began years of bonus extended missions. Both have made important discoveries about wet environments on ancient Mars that may have been favorable for supporting microbial life. Spirit's most recent communication was on March 22, 2010. On the possibility that Spirit may yet awaken from a low-power hibernation status, NASA engineers continue to listen for a signal from that rover.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA's Science Mission Directorate, Washington.

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Wednesday, January 19, 2011

NASA Mars Rover Will Check for Ingredients of Life


Paul Mahaffy, the scientist in charge of the largest instrument on NASA's next Mars rover, watched through glass as clean-room workers installed it into the rover.

The specific work planned for this instrument on Mars requires more all-covering protective garb for these specialized workers than was needed for the building of NASA's earlier Mars rovers.

The instrument is Sample Analysis at Mars, or SAM, built by NASA's Goddard Space Flight Center, Greenbelt, Md. At the carefully selected landing site for the Mars rover named Curiosity, one of SAM's key jobs will be to check for carbon-containing compounds called organic molecules, which are among the building blocks of life on Earth. The clean-room suits worn by Curiosity's builders at NASA's Jet Propulsion Laboratory, Pasadena, Calif., are just part of the care being taken to keep biological material from Earth from showing up in results from SAM.

Organic chemicals consist of carbon and hydrogen and, in many cases, additional elements. They can exist without life, but life as we know it cannot exist without them. SAM can detect a fainter trace of organics and identify a wider variety of them than any instrument yet sent to Mars. It also can provide information about other ingredients of life and clues to past environments.

Researchers will use SAM and nine other science instruments on Curiosity to study whether one of the most intriguing areas on Mars has offered environmental conditions favorable for life and favorable for preserving evidence about whether life has ever existed there. NASA will launch Curiosity from Florida between Nov. 25 and Dec. 18, 2011, as part of the Mars Science Laboratory mission's spacecraft. The spacecraft will deliver the rover to the Martian surface in August 2012. The mission plan is to operate Curiosity on Mars for two years.

"If we don't find any organics, that's useful information," said Mahaffy, of NASA's Goddard Space Flight Center. "That would mean the best place to look for evidence about life on Mars may not be near the surface. It may push us to look deeper." It would also aid understanding of the environmental conditions that remove organics.

"If we do find detectable organics, that would be an encouraging sign that the immediate environment in the rocks we're sampling is preserving these clues," he said. "Then we would use the tools we have to try to determine where the organics may have come from." Organics delivered by meteorites without involvement of biology come with more random chemical structures than the patterns seen in mixtures of organic chemicals produced by organisms.

Mahaffy paused in describing what SAM will do on Mars while engineers and technicians lowered the instrument into its position inside Curiosity this month. A veteran of using earlier spacecraft instruments to study planetary atmospheres, he has coordinated work of hundreds of people in several states and Europe to develop, build and test SAM after NASA selected his team's proposal for it in 2004.

"It has been a long haul getting to this point," he said. "We've taken a set of experiments that would occupy a good portion of a room on Earth and put them into that box the size of a microwave oven."

SAM has three laboratory tools for analyzing chemistry. The tools will examine gases from the Martian atmosphere, as well as gases that ovens and solvents pull from powdered rock and soil samples. Curiosity's robotic arm will deliver the powdered samples to an inlet funnel. SAM's ovens will heat most samples to about 1,000 degrees Celsius (about 1,800 degrees Fahrenheit).

One tool, a mass spectrometer, identifies gases by the molecular weight and electrical charge of their ionized states. It will check for several elements important for life as we know it, including nitrogen, phosphorous, sulfur, oxygen and carbon.

Another tool, a laser spectrometer, uses absorption of light at specific wavelengths to measure concentrations of selected chemicals, such as methane and water vapor. It also identifies the proportions of different isotopes in those gases. Isotopes are variants of the same element with different atomic weights, such as carbon-13 and carbon-12, or oxygen-18 and oxygen-16. Ratios of isotopes can be signatures of planetary processes. For example, Mars once had a much denser atmosphere than it does today, and if the loss occurred at the top of the atmosphere, the process would favor increased concentration of heavier isotopes in the retained, modern atmosphere.

Methane is an organic molecule. Observations from Mars orbit and from Earth in recent years have suggested transient methane in Mars' atmosphere, which would mean methane is being actively added and subtracted at Mars. With SAM's laser spectrometer, researchers will check to confirm whether methane is present, monitor any changes in concentration, and look for clues about whether Mars methane is produced by biological activity or by processes that do not require life. JPL provided SAM's laser spectrometer.

SAM's third analytical tool, a gas chromatograph, separates different gases from a mixture to aid identification. It does some identification itself and also feeds the separated fractions to the mass spectrometer and the laser spectrometer. France's space agency, Centre National d'Études Spatiales, provided support to the French researchers who developed SAM's gas chromatograph.

NASA's investigation of organics on Mars began with the twin Viking landers in 1976. Science goals of more recent Mars missions have tracked a "follow the water" theme, finding multiple lines of evidence for liquid water -- another prerequisite for life -- in Mars' past. The Mars Science Laboratory mission will seek more information about those wet environments, while the capabilities of its SAM instrument add a trailblazing "follow the carbon" aspect and information about how well ancient environments may be preserved.

The original reports from Viking came up negative for organics. How, then, might Curiosity find any? Mahaffy describes three possibilities.

The first is about locations. Mars is diverse, not uniform. Copious information gained from Mars orbiters in recent years is enabling the choice of a landing site with favorable attributes, such as exposures of clay and sulfate minerals good at entrapping organic chemicals. Mobility helps too, especially with the aid of high-resolution geologic mapping generated from orbital observations. The stationary Viking landers could examine only what their arms could reach. Curiosity can use mapped geologic context as a guide in its mobile search for organics and other clues about habitable environments. Additionally, SAM will be able to analyze samples from interiors of rocks drilled into by Curiosity, rather than being restricted to soil samples, as Viking was.

Second, SAM has improved sensitivity, with a capability to detect less than one part-per-billion of an organic compound, over a wider mass range of molecules and after heating samples to a higher temperature.

Third, a lower-heat method using solvents to pull organics from some SAM samples can check a hypothesis that a reactive chemical recently discovered in Martian soil may have masked organics in soil samples baked during Viking tests.

The lower-heat process also allows searching for specific classes of organics with known importance to life on Earth. For example, it can identify amino acids, the chain links of proteins. Other clues from SAM could also be hints about whether organics on Mars -- if detected at all -- come from biological processes or without biology, such as from meteorites. Certain carbon-isotope ratios in organics compared with the ratio in Mars' atmosphere could suggest meteorite origin. Patterns in the number of carbon atoms in organic molecules could be a clue. Researchers will check for a mixture of organics with chains of carbon atoms to see if the mix is predominated either by chains with an even number of carbon atoms or with an odd number. That kind of pattern, rather than a random blend, would be typical of biological assembly of carbon chains from repetitious subunits.

"Even if we see a signature such as mostly even-numbered chains in a mix of organics, we would be hesitant to make any definitive statements about life, but that would certainly indicate that our landing site would be a good place to come back to," Mahaffy said. A future mission could bring a sample back to Earth for more extensive analysis with all the methods available on Earth.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Science Laboratory mission for the NASA Science Mission Directorate, Washington.

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Monday, January 17, 2011

Despite Subtle Differences, Global Temperature Records in Close Agreement


Groups of scientists from several major institutions – NASA’s Goddard Institute for Space Studies (GISS), NOAA's National Climatic Data Center (NCDC), the Japanese Meteorological Agency and the Met Office Hadley Centre in the United Kingdom – tally data collected by temperature monitoring stations spread around the world and make an announcement about whether the previous year was a comparatively warm or cool year.

NASA’s announcement this year – that 2010 ties 2005 as the warmest year in the 131-year instrumental record – made headlines. But, how much does the ranking of a single year matter?

Not all that much, emphasizes James Hansen, the director of NASA’s Goddard Institute for Space Studies (GISS) in New York City. In the GISS analysis, for example, 2010 differed from 2005 by less than 0.01°C (0.018 °F), a difference so small that the temperatures of these two years are indistinguishable, given the uncertainty of the calculation.

Meanwhile, the third warmest year -- 2009 -- is so close to 1998, 2002, 2003, 2006, and 2007, with the maximum difference between the years being a mere 0.03°C, that all six years are virtually tied.

Even for a near record-breaking year like 2010 the broader context is more important than a single year. “Certainly, it is interesting that 2010 was so warm despite the presence of a La Niña and a remarkably inactive sun, two factors that have a cooling influence on the planet, but far more important than any particular year’s ranking are the decadal trends,” Hansen said.

One of the problems with focusing on annual rankings, rather than the longer trend, is that the rankings of individual years often differ in the most closely watched temperature analyses – from GISS, NCDC, and the Met Office – a situation that can generate confusion.

For example, while GISS previously ranked 2005 warmest, the Met Office listed 1998 warmest. The discrepancy helped fuel the misperception that findings from the three groups vary sharply or contain large amounts of uncertainty. It also fueled the misperception that global warming stopped in 1998.

“In reality, nothing could be further from the truth,” said Hansen. Global temperatures have continued to rise steadily. “The three official records vary slightly because of subtle differences in the way we analyze the data, but they agree extraordinarily well,” said Reto Ruedy, one of Hansen’s colleagues at GISS who helps analyze global surface temperatures.

All three records show peaks and valleys that vary in virtual sync with each other since 1880. All three show particularly rapid warming in the last few decades. And all three show the last decade is the warmest in the instrumental record.

Handling the Arctic

There are several reasons for the small discrepancies that exist between the three records. Most important, subtleties in the way the scientists from each institution handle regions of the world where temperature-monitoring stations are scarce produce differences.

While developed areas have a dense network of weather stations, temperature monitoring equipment is sparse in some parts of the Amazon, Africa, Antarctica, and Arctic. In the Arctic, particularly, the absence of solid land means there are large areas without weather stations.

The Met Office and the NCDC leave areas of the Arctic Ocean without stations out of their analyses, while GISS approaches the problem by filling in the gaps with data from the nearest land stations, up to a distance of 1200 kilometers (746 miles) away. In this way, the GISS analysis achieves near total coverage in the Arctic.

Both approaches pose problems. By not inferring data, the Met Office assumes that areas without stations have a warming equal to that experienced by the entire Northern Hemisphere, a value that satellite and field measurements suggest is too low given the rate of Arctic sea ice loss.

On the other hand, GISS’s approach may either overestimate or underestimate Arctic warming. “There’s no doubt that estimates of Arctic warming are uncertain, and should be regarded with caution,” Hansen said. “Still, the rapid pace of Arctic ice retreat leaves little question that temperatures in the region are rising fast, perhaps faster than we assume in our analysis.”

Choosing a Base Period

Another reason that the three records differ relates to the “base period” that each group uses to calculate global temperature changes. It is not possible to calculate absolute global average surface temperatures for the GISS analysis because weather stations aren’t spread evenly enough across the globe to offer meaningful measurements. Scientists instead calculate a relative measure called a “temperature anomaly” to track whether global temperatures are changing.

To calculate temperature anomalies scientists compare average temperatures over any given time period -- a month or year, for example -- to a long-term average, or base period. The base period serves as a point of reference against which climate change can be tracked.

All three groups use this same approach, but they do not all use the same base period. GISS uses a base period of 1951 to 1980. The Met Office uses 1961 to 1990. And NCDC uses the entire 20th century. Average temperatures during the GISS and NCDC base periods are about the same, but the base period the Met Office uses is slightly warmer than the period the other two groups use.

This means that numerical values of the temperature anomalies differ for the three analyses. However, the choice of base period should have no effect on the ranking of different years or on the magnitude of global warming over the past century.

Invariably, a great deal of attention centers on each year’s ranking, but it is critical to focus on the decade-long trends that matter more, the GISS scientists emphasize. On that time scale, the three records are unequivocal: the last decade has been the warmest on record. “It’s not particularly important whether 2010, 2005, or 1998 was the hottest year on record,” said Hansen. "It is the underlying trend that is important."

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Sunday, January 16, 2011

Going Supernova


While searching the skies for black holes using NASA's Spitzer Space Telescope, astronomers discovered a giant supernova that was smothered in its own dust. In this artist's rendering, an outer shell of gas and dust -- which erupted from the star hundreds of years ago -- obscures the supernova within. This event in a distant galaxy hints at one possible future for the brightest star system in our own Milky Way.

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Thursday, January 13, 2011

Cassini's Snaps of Rhea Coming Down


Raw images obtained by NASA's Cassini spacecraft from the closest flyby of Saturn's moon Rhea have begun streaming to Cassini's raw image page.

At closest approach, Cassini glided within about 69 kilometers (43 miles) of Rhea's surface at 4:53 AM UTC on Jan. 11, which was 10:53 PM Pacific Time on Jan. 10.

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Wednesday, January 12, 2011

Cosmology Standard Candle not so Standard After All


Astronomers have turned up the first direct proof that "standard candles" used to illuminate the size of the universe, termed Cepheids, shrink in mass, making them not quite as standard as once thought. The findings, made with NASA's Spitzer Space Telescope, will help astronomers make even more precise measurements of the size, age and expansion rate of our universe.

Standard candles are astronomical objects that make up the rungs of the so-called cosmic distance ladder, a tool for measuring the distances to farther and farther galaxies. The ladder's first rung consists of pulsating stars called Cepheid variables, or Cepheids for short. Measurements of the distances to these stars from Earth are critical in making precise measurements of even more distant objects. Each rung on the ladder depends on the previous one, so without accurate Cepheid measurements, the whole cosmic distance ladder would come unhinged.

Now, new observations from Spitzer show that keeping this ladder secure requires even more careful attention to Cepheids. The telescope's infrared observations of one particular Cepheid provide the first direct evidence that these stars can lose mass—or essentially shrink. This could affect measurements of their distances.

"We have shown that these particular standard candles are slowly consumed by their wind," said Massimo Marengo of Iowa State University, Ames, Iowa, lead author of a recent study on the discovery appearing in the Astronomical Journal. "When using Cepheids as standard candles, we must be extra careful because, much like actual candles, they are consumed as they burn."

The star in the study is Delta Cephei, which is the namesake for the entire class of Cepheids. It was discovered in 1784 in the constellation Cepheus, or the King. Intermediate-mass stars can become Cepheids when they are middle-aged, pulsing with a regular beat that is related to how bright they are. This unique trait allows astronomers to take the pulse of a Cepheid and figure out how bright it is intrinsically—or how bright it would be if you were right next to it. By measuring how bright the star appears in the sky, and comparing this to its intrinsic brightness, it can then be determined how far away it must be.

This calculation was famously performed by astronomer Edwin Hubble in 1924, leading to the revelation that our galaxy is just one of many in a vast cosmic sea. Cepheids also helped in the discovery that our universe is expanding and galaxies are drifting apart.

Cepheids have since become reliable rungs on the cosmic distance ladder, but mysteries about these standard candles remain. One question has been whether or not they lose mass. Winds from a Cepheid star could blow off significant amounts of gas and dust, forming a dusty cocoon around the star that would affect how bright it appears. This, in turn, would affect calculations of its distance. Previous research had hinted at such mass loss, but more direct evidence was needed.

Marengo and his colleague used Spitzer's infrared vision to study the dust around Delta Cephei. This particular star is racing along through space at high speeds, pushing interstellar gas and dust into a bow shock up ahead. Luckily for the scientists, a nearby companion star happens to be lighting the area, making the bow shock easier to see. By studying the size and structure of the shock, the team was able to show that a strong, massive wind from the star is pushing against the interstellar gas and dust. In addition, the team calculated that this wind is up to one million times stronger than the wind blown by our sun. This proves that Delta Cephei is shrinking slightly.

Follow-up observations of other Cepheids conducted by the same team using Spitzer have shown that other Cepheids, up to 25 percent observed, are also losing mass.

"Everything crumbles in cosmology studies if you don't start up with the most precise measurements of Cepheids possible," said Pauline Barmby of the University of Western Ontario, Canada, lead author of the follow-up Cepheid study published online Jan. 6 in the Astronomical Journal. "This discovery will allow us to better understand these stars, and use them as ever more precise distance indicators."

Other authors of this study include N. R. Evans and G.G. Fazio of the Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass.; L.D. Matthews of Harvard-Smithsonian and the Massachusetts Institute of Technology Haystack Observatory, Westford; G. Bono of the Università di Roma Tor Vergata and the INAF-Osservatorio Astronomico di Roma in Rome, Italy; D.L. Welch of the McMaster University, Ontario, Canada; M. Romaniello of the European Southern Observatory, Garching, Germany; D. Huelsman of Harvard-Smithsonian and University of Cincinnati, Ohio; and K. Y. L. Su of the University of Arizona, Tucson.

The Spitzer observations were made before it ran out of its liquid coolant in May 2009 and began its warm mission.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology, also in Pasadena.

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Tuesday, January 11, 2011

NASA Radar Reveals Features on Asteroid


Radar imaging at NASA's Goldstone Solar System Radar in the California desert on Dec. 11 and 12, 2010, revealed defining characteristics of recently discovered asteroid 2010 JL33. The images have been made into a short movie that shows the celestial object's rotation and shape. A team led by Marina Brozovic, a scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., made the discovery.

"Asteroid 2010 JL33 was discovered on May 6 by the Mount Lemmon Survey in Arizona, but prior to the radar observations, little was known about it," said Lance Benner, a scientist at JPL. "By using the Goldstone Solar System Radar, we can obtain detailed images that reveal the asteroid's size, shape and rotational rate, improve its orbit, and even make out specific surface features."

Data from the radar reveal 2010 JL33 to be an irregular, elongated object roughly 1.8 kilometers (1.1 miles) wide that rotates once every nine hours. The asteroid's most conspicuous feature is a large concavity that may be an impact crater. The images in the movie span about 90 percent of one rotation.

At the time it was imaged, the asteroid was about 22 times the distance between Earth and the moon (8.5 million kilometers, or 5.3 million miles). At that distance, the radio signals from the Goldstone radar dish used to make the images took 56 seconds to make the roundtrip from Earth to the asteroid and back to Earth again.

The 70-meter (230-foot) Goldstone antenna in California's Mojave Desert, part of NASA's Deep Space network, is one of only two facilities capable of imaging asteroids with radar. The other is the National Science Foundation’s 1,000-foot-diameter (305 meters) Arecibo Observatory in Puerto Rico. The capabilities of the two instruments are complementary. The Arecibo radar is about 20 times more sensitive, can see about one-third of the sky, and can detect asteroids about twice as far away. Goldstone is fully steerable, can see about 80 percent of the sky, can track objects several times longer per day, and can image asteroids at finer spatial resolution. To date, Goldstone and Arecibo have observed 272 near-Earth asteroids and 14 comets with radar. JPL manages the Goldstone Solar System Radar and the Deep Space Network for NASA.

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Monday, January 10, 2011

NASA's Hubble Finds that Puny Stars Pack a Big Punch


A deep survey of more than 200,000 stars in our Milky Way galaxy has unveiled the sometimes petulant behavior of tiny red dwarf stars. These stars, which are smaller than the Sun, can unleash powerful eruptions called flares that may release the energy of more than 100 million atomic bombs.

Red dwarfs are the most abundant stars in our universe and are presumably hosts to numerous planets. However, their erratic behavior could make life unpleasant, if not impossible, for many alien worlds. Flares are sudden eruptions of heated plasma that occur when powerful magnetic field lines in a star's atmosphere "reconnect," snapping like a rubber band and releasing vast amounts of energy. When they occur, flares would blast any planets orbiting the star with ultraviolet light, bursts of X-rays, and a gush of charged particles called a stellar wind.

Studying the light from 215,000 red dwarfs collected in observations by NASA's Hubble Space Telescope, astronomers found 100 stellar flares. The observations, taken over a seven-day period, constitute the largest continuous monitoring of red dwarf stars ever undertaken.

"We know that hyperactive young stars produce flares, but this study shows that even in fairly old stars that are several billion years old, flares are a fact of life," says astronomer Rachel Osten of the Space Telescope Science Institute in Baltimore, Md., leader of the research team. "Life could be rough for any planets orbiting close enough to these flaring stars. Their heated atmospheres could puff up and might get stripped away."

Osten and her team, including Adam Kowalski of the University of Washington in Seattle, found that the red dwarf stars flared about 15 times less frequently than in previous surveys, which observed younger and less massive stars.

The stars in this study were originally part of a search for planets. Hubble monitored the stars continuously for a week in 2006, looking for the signature of planets passing in front of them. The stars were photographed by Hubble's Advanced Camera for Surveys during the extrasolar-planet survey called the Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS).

Osten and Kowalski realized that this powerful census contained important information on the stars themselves, and they took advantage of it. They searched the Hubble data, looking for a slight increase in the brightness of red dwarfs, a signature of flares. Some of the stars grew up to 10 percent brighter over a short period of time, which is actually much brighter than flares on our Sun. The average duration of the flares was 15 minutes. A few stars produced multiple flares.

The astronomers found that stars that periodically oscillate in brightness, called variable stars, were more prone to the short-term outbursts.

"We discovered that variable stars are about a thousand times more likely to flare than non-variable stars," Kowalski says. "The variable stars are rotating fast, which may mean they are in rapidly orbiting binary systems. If the stars possess large star spots, dark regions on a star's surface, that will cause the star's light to vary when the spots rotate in and out of view. Star spots are produced when magnetic field lines poke through the surface. So, if there are big spots, there is a large area covered by strong magnetic fields, and we found that those stars had more flares."

Although red dwarfs are smaller than the Sun, they have a deeper convection zone, where cells of hot gas bubble to the surface, like boiling oatmeal," Osten explains. This zone generates the magnetic field and enables red dwarfs to put out such energetic flares.

"The red dwarfs also have magnetic fields that are stronger than the Sun's," Osten continues. "They cover a much larger area than the Sun. Sunspots cover less than 1 percent of the Sun's surface, while red dwarfs can have star spots that cover half of their surfaces."

Kowalski will present the team's results on Jan. 10, 2011, at the American Astronomical Society meeting in Seattle, Wash.

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Sunday, January 9, 2011

Exoplanets, Dwarf Stars, Gamma-Ray Flashes, New Images Among NASA News Highlights At American Astronomical Society Meeting

NASA researchers will present new findings on a wide range of space science topics during the meeting of the American Astronomical Society. The meeting runs Sunday, Jan. 9, through Thursday, Jan. 13, at the Washington State Convention and Trade Center, located at 800 Convention Place in Seattle.

Media briefings during the conference will discuss new results on exoplanet research, dwarf stars, gamma-ray flashes and black holes. New images will be released from missions including the Hubble Space Telescope; the Wide-Field Infrared Survey Explorer, or WISE; the Chandra X-ray Observatory; and the Stratospheric Observatory for Infrared Astronomy, or SOFIA. NASA scientists and their colleagues who use NASA research capabilities will present noteworthy findings during scientific sessions that are open to registered journalists.

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Friday, January 7, 2011

Stirring Up a Bloom Off Patagonia

Off the coast of Argentina, two strong ocean currents recently stirred up a colorful brew of floating nutrients and microscopic plant life just in time for the Southern Hemisphere's summer solstice. The Moderate Resolution Imaging Spectroradiometer on NASA’s Aqua satellite captured this image of a massive phytoplankton bloom off of the Atlantic coast of Patagonia on Dec. 21, 2010. Scientists used seven separate spectral bands to highlight the differences in the plankton communities across this swath of ocean.

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Thursday, January 6, 2011

NASA Research Team Reveals Moon Has Earth-Like Core


State-of-the-art seismological techniques applied to Apollo-era data suggest our moon has a core similar to Earth's.

Uncovering details about the lunar core is critical for developing accurate models of the moon's formation. The data sheds light on the evolution of a lunar dynamo -- a natural process by which our moon may have generated and maintained its own strong magnetic field.

The team's findings suggest the moon possesses a solid, iron-rich inner core with a radius of nearly 150 miles and a fluid, primarily liquid-iron outer core with a radius of roughly 205 miles. Where it differs from Earth is a partially molten boundary layer around the core estimated to have a radius of nearly 300 miles. The research indicates the core contains a small percentage of light elements such as sulfur, echoing new seismology research on Earth that suggests the presence of light elements -- such as sulfur and oxygen -- in a layer around our own core.

The researchers used extensive data gathered during the Apollo-era moon missions. The Apollo Passive Seismic Experiment consisted of four seismometers deployed between 1969 and 1972, which recorded continuous lunar seismic activity until late-1977.

"We applied tried and true methodologies from terrestrial seismology to this legacy data set to present the first-ever direct detection of the moon's core," said Renee Weber, lead researcher and space scientist at NASA's Marshall Space Flight Center in Huntsville, Ala.

In addition to Weber, the team consisted of scientists from Marshall; Arizona State University; the University of California at Santa Cruz; and the Institut de Physique du Globe de Paris in France. Their findings are published in the online edition of the journal Science.

The team also analyzed Apollo lunar seismograms using array processing, techniques that identify and distinguish signal sources of moonquakes and other seismic activity. The researchers identified how and where seismic waves passed through or were reflected by elements of the moon's interior, signifying the composition and state of layer interfaces at varying depths.

Although sophisticated satellite imaging missions to the moon made significant contributions to the study of its history and topography, the deep interior of Earth's sole natural satellite remained a subject of speculation and conjecture since the Apollo era. Researchers previously had inferred the existence of a core, based on indirect estimates of the moon's interior properties, but many disagreed about its radius, state and composition.

A primary limitation to past lunar seismic studies was the wash of "noise" caused by overlapping signals bouncing repeatedly off structures in the moon's fractionated crust. To mitigate this challenge, Weber and the team employed an approach called seismogram stacking, or the digital partitioning of signals. Stacking improved the signal-to-noise ratio and enabled the researchers to more clearly track the path and behavior of each unique signal as it passed through the lunar interior.

"We hope to continue working with the Apollo seismic data to further refine our estimates of core properties and characterize lunar signals as clearly as possible to aid in the interpretation of data returned from future missions," Weber said.

Future NASA missions will help gather more detailed data. The Gravity Recovery and Interior Laboratory, or GRAIL, is a NASA Discovery-class mission set to launch this year. The mission consists of twin spacecraft that will enter tandem orbits around the moon for several months to measure the gravity field in unprecedented detail. The mission also will answer longstanding questions about Earth's moon and provide scientists a better understanding of the satellite from crust to core, revealing subsurface structures and, indirectly, its thermal history.

NASA and other space agencies have been studying concepts to establish an International Lunar Network -- a robotic set of geophysical monitoring stations on the moon -- as part of efforts to coordinate international missions during the coming decade.

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Wednesday, January 5, 2011

NASA Tests New Propulsion System For Robotic Lander Prototype


NASA's Robotic Lunar Lander Development Project at Marshall Space Flight Center in Huntsville, Ala., has completed a series of hot fire tests and taken delivery of a new propulsion system for integration into a more sophisticated free-flying autonomous robotic lander prototype. The project is partnered with the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., to develop a new generation of small, smart, versatile robotic landers to achieve scientific and exploration goals on the surface of the moon and near-Earth asteroids.

The new robotic lander prototype will continue to mature the development of a robotic lander capability by bringing online an autonomous flying test lander that will be capable of flying up to sixty seconds, testing the guidance, navigation and control system by demonstrating a controlled landing in a simulated low gravity environment.

By the spring of 2011, the new prototype lander will begin flight tests at the U.S. Army's Redstone Arsenal Test Center in Huntsville, Ala.

The prototype’s new propulsion system consists of 12 small attitude control thrusters, three primary descent thrusters to control the vehicle’s altitude, and one large "gravity-canceling" thruster which offsets a portion of the prototype’s weight to simulate a lower gravity environment, like that of the moon and asteroids. The prototype uses a green propellant, hydrogen peroxide, in a stronger concentration of a solution commonly used in homes as a disinfectant. The by-products after use are water and oxygen.

"The propulsion hardware acceptance test consisted of a series of tests that verified the performance of each thruster in the propulsion system," said Julie Bassler, Robotic Lunar Lander Development Project Manager. "The series culminated in a test that characterized the entire system by running a scripted set of thruster firings based on a flight scenario simulation."

The propulsion system is currently at Teledyne Brown’s manufacturing facility in Huntsville, Ala., for integration with the structure and avionics to complete the new robotic lander prototype. Dynetics Corp. developed the robotic lander prototype propulsion system under the management of the Von Braun Center for Science and Innovation both located in Huntsville, Ala.

"This is the second phase of a robotic lander prototype development program," said Bassler. "Our initial "cold gas" prototype was built, delivered and successfully flight tested at the Marshall Center in a record nine months, providing a physical and tangible demonstration of capabilities related to the critical terminal descent and landing phases for an airless body mission."

The first robotic lander prototype has a record flight time of ten seconds and descended from three meters altitude. This first robotic lander prototype began flight tests in September 2009 and has completed 142 flight tests, providing a platform to develop and test algorithms, sensors, avionics, ground and flight software and ground systems to support autonomous landings on airless bodies, where aero-braking and parachutes are not options.

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Tuesday, January 4, 2011

Developers Support JPL-Led Software Architecture


The Object Oriented Data Technology (OODT) architecture, originally developed at NASA's Jet Propulsion Laboratory, Pasadena, Calif., was recently selected to become a fully-fledged Top Level Project at the Apache Software Foundation, Forest Hill, Md. This important recognition means that OODT will be one of the few projects to receive project management and resource support from the open-source software foundation.

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Monday, January 3, 2011

The Road Less Traveled


On Jan. 4, 2004, Spirit--the first of two NASA Mars Exploration Rovers--landed on the Red Planet for what was to be a 90-day mission. This image, acquired on sol 127 (May 12, 2004), shows the path the rover traveled on its way to the base of the "Columbia Hills." The hills can be seen silhouetted against the horizon on the far left side .

Since sol 2210 (March 22, 2010), Spirit has been silent, and the project's scientists continue to listen for Spirit with the Deep Space Network and Mars Odyssey orbiter. The project is also conducting a paging technique called "Sweep & Beep" to stimulate the rover. Since the period of peak solar activity occurs in mid-March 2011, leaving Spirit plenty of occasion to respond. Spirit's sister spacecraft Opportunity continues to explore Mars, arriving in December 2010 at the 80-meter (262-foot) diameter Santa Maria crater on its journey to Endeavour crater.

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Sunday, January 2, 2011

Semisopochnoi Island, Alaska


It is the “Island of the Seven Mountains, ” or more precisely in Russian: “having seven hills.” This uninhabited volcanic island is also an important nesting area for maritime birds of the North Pacific.

Situated on the far end of the Aleutians, Semisopochnoi Island is simultaneously the most easterly and westerly point of the United States of America. Roughly 1,275 miles (2,050 kilometers) west-southwest of Anchorage, Alaska, Semisopochnoi lies near the 180-degree line of longitude, in the Rat Islands group in the western Aleutian Islands.

This pseudo-true color image was acquired on June 22, 2000, by the Enhanced Thematic Mapper Plus (ETM+) on Landsat 7. Colors are what you would expect: snow is white, bare ground is tan, water is blue, clouds are grey, and vegetation is green.

The seven hills of the island are volcanic peaks, each with a summit crater, including Cerberus, Sugarloaf Peak, Lakeshore Cone, Anvil Peak, Pochnoi, Ragged Top, and Three-quarter Cone. The high point of the island is Anvil Peak at 1,221 meters, a double-peaked cone. The three-peaked Mount Cerberus volcano (774 meters high) grew up within the caldera as the volcanic hot spot rose up from the sea floor. Most documented eruptions have come from Cerberus, with the most recent major eruption recorded in 1873. The most recent eruption on the island, though minor, came from Sugarloaf in 1987.

Semisopochnoi has no native land mammals, so it is a natural nesting area for sea birds. But bird populations were decimated after Arctic foxes were introduced to the island for fur farming in the 19th century. In 1997, the last fox was removed from the island to allow the birds a safe refuge again. Part of the Alaska Maritime National Wildlife Refuge (AMNWR), the island now supports more than a million seabirds, particularly auklets, according to the National Audubon Society.

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